The great thing about a low-sodium salt substitute, aside from the fact that
it is measurably radioactive, is that people put it on their food!Not to worry – consuming a salt substitute doesn’t increase your
radiation exposure.

Salt substitutes are radioactive because they contain
potassium chloride, and all potassium contains the radioactive beta-gamma
emitter potassium-40. For some additional information about K-40, click here.

Salt substitutes vary in their composition, but their
main ingredient is always potassium chloride. For
example, the listed contents of the Nu-Salt are: potassium chloride, cream
of tartar, drier and natural flavor derived from yeast. Contains less than
20 mg of sodium per 100 grams.
The contents of the NoSalt are: potassium chloride, potassium bitartrate,
adipic acid, mineral oil, fumaric acid and silicon dioxide. The ingredients
of another salt substitute, not shown here, are: potassium chloride,
L-glutamic acid, mono-potassium glutamate, tri-calcium phosphate and
0.01%potassium iodide.

A salt substitute does not taste exactly like sodium chloride, but it is
similar enough, and it contains less or none of the sodium that some
people are trying to avoid.

To measure the activity of a low sodium salt, pour some onto a piece of
paper (the paper makes it easier to get the salt back into the container).
The idea is to detect the K-40 beta particles rather than the gamma rays,
and getting the salt out of the container helps in this regard. Be sure to
use plenty of “salt,” e.g., 5-10 grams.Perhaps the best readily available detector to use is a thin window
Geiger Mueller detector (e.g., a pancake GM). A detector with an audio
output that is nice and loud makes for a better demonstration. Before you
make the actual measurement, listen to the background for a while. Then,
when the suspense is just about to become unbearable, quickly move the
probe onto the surface of the salt. If the gods are smiling, the count
rate should more than double. Finally, don’t forget to clean the probe
after the demonstration since residual salt substitute will increase the
background.